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Molecular insights into Zeaxanthin-dependent quenching in higher plants.

Xu P, Tian L, Kloz M, Croce R - Sci Rep (2015)

Bottom Line: We show that small amounts of zeaxanthin are associated with the complexes, but in contrast to what is generally believed, zeaxanthin binding per se does not cause conformational changes in the complexes and does not induce quenching, not even at low pH.We show that in NPQ conditions zeaxanthin does not exchange for violaxanthin in the internal binding sites of the antennas but is located at the periphery of the complexes.These results together with the observation that the zeaxanthin-dependent quenching is active in isolated membranes, but not in functional supercomplexes, suggests that zeaxanthin is acting in between the complexes, helping to create/participating in a variety of quenching sites.

View Article: PubMed Central - PubMed

Affiliation: Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam and LaserLab Amsterdam. De Boelelaan, 1081, 1081 HV, Amsterdam, The Netherlands.

ABSTRACT
Photosynthetic organisms protect themselves from high-light stress by dissipating excess absorbed energy as heat in a process called non-photochemical quenching (NPQ). Zeaxanthin is essential for the full development of NPQ, but its role remains debated. The main discussion revolves around two points: where does zeaxanthin bind and does it quench? To answer these questions we have followed the zeaxanthin-dependent quenching from leaves to individual complexes, including supercomplexes. We show that small amounts of zeaxanthin are associated with the complexes, but in contrast to what is generally believed, zeaxanthin binding per se does not cause conformational changes in the complexes and does not induce quenching, not even at low pH. We show that in NPQ conditions zeaxanthin does not exchange for violaxanthin in the internal binding sites of the antennas but is located at the periphery of the complexes. These results together with the observation that the zeaxanthin-dependent quenching is active in isolated membranes, but not in functional supercomplexes, suggests that zeaxanthin is acting in between the complexes, helping to create/participating in a variety of quenching sites. This can explain why none of the antennas appears to be essential for NPQ and the multiple quenching mechanisms that have been observed in plants.

No MeSH data available.


Related in: MedlinePlus

Absorption and Circular Dichroism spectra.(a) Absorption and (b) Circular Dichroism spectra of pigment-protein complexes and supercomplexes as indicated in the figures. The absorption spectra are normalized to the maximum in the Qy region and the CD spectra are normalized to the absorption.
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f3: Absorption and Circular Dichroism spectra.(a) Absorption and (b) Circular Dichroism spectra of pigment-protein complexes and supercomplexes as indicated in the figures. The absorption spectra are normalized to the maximum in the Qy region and the CD spectra are normalized to the absorption.

Mentions: The purity of the isolated complexes was confirmed by SDS-page (Fig. 2b). The absorption (Fig. 3a) and circular dichroism (CD, Fig. 3b) spectra of the same complexes purified from control and light-stressed plants were virtually identical in the Chl absorption region indicating that the stress does not induce differences in their Chl composition and organization. Small changes were visible in the blue absorption region, in agreement with changes in the carotenoid composition upon light stress.


Molecular insights into Zeaxanthin-dependent quenching in higher plants.

Xu P, Tian L, Kloz M, Croce R - Sci Rep (2015)

Absorption and Circular Dichroism spectra.(a) Absorption and (b) Circular Dichroism spectra of pigment-protein complexes and supercomplexes as indicated in the figures. The absorption spectra are normalized to the maximum in the Qy region and the CD spectra are normalized to the absorption.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555179&req=5

f3: Absorption and Circular Dichroism spectra.(a) Absorption and (b) Circular Dichroism spectra of pigment-protein complexes and supercomplexes as indicated in the figures. The absorption spectra are normalized to the maximum in the Qy region and the CD spectra are normalized to the absorption.
Mentions: The purity of the isolated complexes was confirmed by SDS-page (Fig. 2b). The absorption (Fig. 3a) and circular dichroism (CD, Fig. 3b) spectra of the same complexes purified from control and light-stressed plants were virtually identical in the Chl absorption region indicating that the stress does not induce differences in their Chl composition and organization. Small changes were visible in the blue absorption region, in agreement with changes in the carotenoid composition upon light stress.

Bottom Line: We show that small amounts of zeaxanthin are associated with the complexes, but in contrast to what is generally believed, zeaxanthin binding per se does not cause conformational changes in the complexes and does not induce quenching, not even at low pH.We show that in NPQ conditions zeaxanthin does not exchange for violaxanthin in the internal binding sites of the antennas but is located at the periphery of the complexes.These results together with the observation that the zeaxanthin-dependent quenching is active in isolated membranes, but not in functional supercomplexes, suggests that zeaxanthin is acting in between the complexes, helping to create/participating in a variety of quenching sites.

View Article: PubMed Central - PubMed

Affiliation: Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam and LaserLab Amsterdam. De Boelelaan, 1081, 1081 HV, Amsterdam, The Netherlands.

ABSTRACT
Photosynthetic organisms protect themselves from high-light stress by dissipating excess absorbed energy as heat in a process called non-photochemical quenching (NPQ). Zeaxanthin is essential for the full development of NPQ, but its role remains debated. The main discussion revolves around two points: where does zeaxanthin bind and does it quench? To answer these questions we have followed the zeaxanthin-dependent quenching from leaves to individual complexes, including supercomplexes. We show that small amounts of zeaxanthin are associated with the complexes, but in contrast to what is generally believed, zeaxanthin binding per se does not cause conformational changes in the complexes and does not induce quenching, not even at low pH. We show that in NPQ conditions zeaxanthin does not exchange for violaxanthin in the internal binding sites of the antennas but is located at the periphery of the complexes. These results together with the observation that the zeaxanthin-dependent quenching is active in isolated membranes, but not in functional supercomplexes, suggests that zeaxanthin is acting in between the complexes, helping to create/participating in a variety of quenching sites. This can explain why none of the antennas appears to be essential for NPQ and the multiple quenching mechanisms that have been observed in plants.

No MeSH data available.


Related in: MedlinePlus